ADEN/GENEVA (Reuters) - The Saudi-led military coalition fighting against Yemen’s Houthi movement reopened a land border crossing, partly easing a blockade imposed earlier this week, but aid agencies warned of famine and a health catastrophe if other ports stay shut.

The coalition said on Monday it would close all air, land and sea ports in Yemen to stem the flow of arms to the Houthis from Iran, after Saudi Arabia intercepted a missile fired towards its capital Riyadh.

The al Wadea border crossing, linking Saudi Arabia with territory in eastern Yemen controlled by the Saudi-backed government, was reopened on Thursday, a Yemeni official and witnesses said, letting food and other supplies across.

The United Nations has said that a total blockade of Yemen could cause a famine that could kill millions. The government-held southern port of Aden was reopened on Wednesday, but ports in Houthi-held areas are still shut.

The Houthis, drawn mainly from Yemen’s Zaidi Shi‘ite minority and allied to long-serving former president Ali Abdullah Saleh, control much of the country including the capital San‘aa. Saudi Arabia and its Arab allies have been waging war against them on behalf of the government of President Abd-Rabbu Mansour Hadi, based in Aden.

The Saudis and their allies say the Houthis get weapons from their arch-foe, Iran. Iran denies arming the Houthis and blames the conflict in Yemen on Riyadh.

FUEL AND VACCINES RUNNING OUT

Yemen’s stocks of fuel and vaccines will run out in a month unless the Saudi-led coalition allows aid into the blockaded port of Hodeidah and the airport at San‘aa, UNICEF’s representative in the country said on Friday.

Meritxell Relano, speaking by phone to reporters in Geneva, said fuel prices had risen 60 percent and there were urgent concerns about a diphtheria outbreak, as well as food shortages because of the port closure.

“The situation that was already catastrophic is just getting worse,” she said. “The impact of this is unimaginable in terms of health and diseases.”

After two years of civil war, Yemen has 7 million people on the brink of famine and has had 900,000 suspected cholera cases in the past six months.

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United Nations aid chief Mark Lowcock said on Wednesday that if the coalition did not allow humanitarian aid access to Yemen, it would cause “the largest famine the world has seen for many decades, with millions of victims.”

The cholera epidemic had abated in recent weeks with the number of cases slowing amid a major push to fight the disease. But the World Health Organization said the progress could be reversed by the blockade.

“If the closure is not stopped in the coming days, we may see that the progress is stopped,” WHO spokeswoman Fadela Chaib told a briefing in Geneva. “We can see even more cases and more deaths as a result of not being able to get access to people.”

The closure of Hodeidah port prevented a ship setting sail from Djibouti with 250 tonnes of WHO medical supplies on Wednesday. Trauma kits in particular are running short.

“If the hostilities continue and the ports remain closed, we will not be able to perform life-saving surgeries or provide basic healthcare,” Chaib said.

Germany will double its aid to UNICEF for Yemen to 20 million euros this year to help deal with looming famine, bringing its total annual aid to Yemen to 70 million, a spokeswoman for the development ministry said on Friday.

“The suffering of the people in Yemen is inconceivable and it threatens to become much worse,” Development Minister Gerd Mueller told Passauer Neue Presse newspaper. “We must act now to prevent the death by starvation of millions of women, children and men.”